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Tahoe / Yukon Service Manual

Forward Collision Alert System Malfunction (without UGN)

Diagnostic Instructions Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Review Strategy Based Diagnosis for an overview of the diagnostic approach. Diagnostic Procedure Instructions provides an overview of each diagnostic category. Diagnostic Fault Information

Circuit Number Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performan
5737 Signal 2 2 2 —
1449 Low Reference — 1 — —
639 Ignition 3 3 — —
1851 Ground — 3 — —
3885 Control 3 3 3 —
4787 Control 4 4 4 —
1. Cruise control inoperative 2. Unable to change forward collision alert sensitivity 3. Forward collision alert indicators inoperative 4. Forward collision alert indicators do not dim properly – Indicators may be excessively bright or dim

Circuit/System Description For an overview of the adaptive cruise control system, refer to Forward Collision Alert Description and Operation. Diagnostic Aids Certain factors will affect the operation of the forward collision alert system. Forward collision alert is intended to detect vehicles. It is not intended to warn the driver of any objects that are not detected as a vehicle such as animals, signs, guard rails, bridges, construction barrels, or other stationary or slow moving objects. In some cases the B174W Front View Camera - Windshield may inadvertently detect a vehicle that is not in the path ahead or the system may occasionally provide unrealistic alerts. This could occur with a turning vehicle ahead, guard rails, traffic signs, or other stationary objects. This is normal operation and the vehicle does not need service. Forward collision alert warnings will not occur unless the forward collision alert system detects a vehicle ahead. When a vehicle is detected, the vehicle ahead indicator will display green. Vehicles may not be detected on curves, highway exit ramps, or hills, due to poor visibility; or if a vehicle ahead is partially blocked by pedestrians or other objects. Forward collision alert will not detect another vehicle ahead until it is completely in the driving lane. The B174W Front View Camera - Windshield may have trouble functioning under the following scenarios: Dirty windshield glass or obstruction on windshield. This may included dirt, snow, or ice, a tinted windshield, windshield tint strips, or vinyl strips or graphics on the windshield. Additionally, other obstructions such as brush guards or hood deflectors may obstruct view of the B174W  Camera – Windshield and hinder it’s ability to identify objects, vehicles, and lane markings. The B174W Frontview Camera – Windshield is not properly installed. Verify it is snapped into tabs and is secure. Ensure the bracket is in the correct location by comparing to a known good vehicle. This is especially important if the windshield was recently replaced. Some aftermarket windshield may have the B174W Frontview Camera – Windshield in the incorrect location. Improper installation of a replacement windshield may also prevent completion of the learn if the windshield was not centered and leveled in the vehicle’s windshield opening. Driving through snow or fog, or driving directly into the sun. Driving on windy or hilly roads. Reference Information Schematic Reference Driver Assistance Systems Schematics Connector End View Reference Master Electrical Component List Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References Circuit/System Verification Without UV6

  1. Ignition ON.
  2. Verify there are no DTCs set related to the forward collision alert or lane keep assist system ⇒ If any DTC’s are set Refer to Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If no DTC’s are set
  3. Through vehicle personalization, the forward collision alert system can be set to Off, which disables the system, to Alert, which will only provide an audible or haptic feedback with a visual indicator, or to Alert and Brake, which will provide an alert and apply automatic emergency braking. Verify vehicle personalization is configured in accordance with the customer’s expectations of system operation. ⇒ If vehicle personalization is not configured in accordance with customer expectations, such as the vehicle being configured to Off or Alert, but the customer is expecting automatic emergency braking Enable the feature in vehicle configuration and discuss with the customer the different operating configurations available through vehicle personalization ⇒ If vehicle personalization is set to Alert or Alert and Brake and the system is functioning, but is not providing a visual indicator in the event of an alert Refer to Circuit/System Testing – Test 2 ⇓ If vehicle personalization is configured in accordance with customer expectations
  4. Verify the B174W Front View Camera - Windshield is properly installed. Refer to Diagnostic Aids for details about identifying a properly installed B174W Front View Camera - Windshield. ⇒ If the B174W Front View Camera - Windshield is not properly installed Repair as necessary ⇓ If the B174W Front View Camera - Windshield is properly installed
  5. Verify the area on the windshield in front of the B174W Front View Camera - Windshield is not blocked. Refer to Diagnostic Aids for details about identifying a blocked B174W Front View Camera - Windshield. ⇒ If the windshield is blocked Repair as necessary ⇓ If the windshield is not blocked
  6. Press and release the forward collision alert sensitivity switch. Verify the forward collision alert sensitivity displayed on the P9 Driver Information Center Display changes between, far, medium, near, and off with each press of the switch. ⇒ If the sensitivity does not change Refer to Circuit/System Testing – Test 1 ⇓ If the sensitivity changes
  7. A fault is currently not present and may be an intermittent condition. Refer to Diagnostic Aids. With UV6
  8. Ignition ON.
  9. Verify there are no DTCs set related to the Forward Collision Alert or Lane Keep Assist system ⇒ If any DTC’s are set Refer to Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If no DTC’s are set
  10. Verify the B174W Front View Camera - Windshield is properly installed. Refer to Diagnostic Aids for details about identifying a properly installed B174W Front View Camera - Windshield. ⇒ If the B174W Front View Camera - Windshield is not properly installed Repair as necessary ⇓ If the B174W Front View Camera - Windshield is properly installed
  11. Verify the area on the windshield in front of the B174W Front View Camera - Windshield is not blocked. Refer to Diagnostic Aids for details about identifying a blocked B174W Front View Camera - Windshield. ⇒ If the windshield is blocked Repair as necessary ⇓ If the windshield is not blocked
  12. Press and release the forward collision alert sensitivity switch. Verify the forward collision alert sensitivity displayed on the P9 Driver Information Center Display changes between, far, medium, near, and off with each press of the switch. ⇒ If the sensitivity does not change Refer to Circuit/System Testing – Test 1 ⇓ If the sensitivity changes
  13. A fault is currently not present and may be an intermittent condition. Refer to Diagnostic Aids. Circuit/System Testing Test 1
  14. Ignition OFF, disconnect the X2 and X4 connectors at the K9 Body Control Module, Ignition ON.
  15. Test for less than 1 V between signal circuit terminal 13 X2 and ground. ⇒ If 1 V or greater Repair the short to voltage on circuit 5737. ⇓ If less than 1 V
  16. Ignition OFF
  17. Test for infinite resistance between signal circuit terminal 13 X2 and ground. ⇒ If less than infinite resistance 4.1. Test circuit 5737 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 4.2. Replace the S70L Steering Wheel Controls Switch - Left. ⇓ If infinite resistance
  18. Test for 14.0 k to 14.5 kΩ between signal circuit terminal 13 X2 and low reference circuit terminal 3 X4. ⇒ If not between 14.0 k and 14.5 kΩ 5.1. Test circuit 5737 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 5.2. Test circuit 1449 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 5.3. Replace the S70L Steering Wheel Controls Switch - Left. ⇓ If between 14.0 k and 14.5 kΩ
  19. Test for 3.3 k to 3.7 kΩ between signal circuit terminal 13 X2 and low reference circuit terminal 3 X4 while pressing and holding the adaptive cruise control gap switch. ⇒ If not between 3.3 k and 3.7 kΩ Replace the S70L Steering Wheel Controls Switch - Left. ⇓ If between 3.3 k and 3.7 kΩ
  20. Replace the K9 Body Control Module. Test 2
  21. Ignition OFF, disconnect the connector at the P43 Collision Alert Indicators.
  22. Verify a test lamp illuminates between ground circuit terminal 4 and B+ ⇒ If the test lamp does not illuminate Repair the open/high resistance on circuit 1851 or the ground connection. ⇓ If the test lamp illuminates
  23. Ignition ON.
  24. Verify a test lamp illuminates between ignition circuit terminal 1 and ground. ⇒ If the test lamp does not turn illuminate and the circuit fuse is OK 4.1. Ignition OFF, remove the test lamp. 4.2. Test circuit 639 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 4.3. Verify the fuse is OK and there is voltage at the fuse. Refer to Power Mode Mismatch. ⇒ If the test lamp does not turn On and the circuit fuse is open 4.1. Ignition OFF, remove the test lamp. 4.2. Test circuit 639 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found
  1. Ignition OFF, disconnect the X1 connector at the P16 Instrument Cluster, ignition ON.
  2. Test for less than 1 V between control circuit terminal 11 at the P16 Instrument Cluster connector and ground. ⇒ If 1 V or greater Repair the short to voltage on circuit 4787. ⇓ If less than 1 V
  3. Test for less than 1 V between control circuit terminal 12 at the P16 Instrument Cluster connector and ground. ⇒ If 1 V or greater Repair the short to voltage on circuit 3885. ⇓ If less than 1 V
  4. Ignition OFF.
  5. Test for infinite resistance between control circuit terminal 11 at the P16 Instrument Cluster connector and ground. ⇒ If less than infinite resistance Repair the short to ground on circuit 4787. ⇓ If infinite resistance
  6. Test for infinite resistance between control circuit terminal 12 at the P16 Instrument Cluster connector and ground. ⇒ If less than infinite resistance Repair the short to ground on circuit 3885. ⇓ If infinite resistance
  7. Test for less than 2 Ω between control circuit terminal 11 at the P16 Instrument Cluster connector and control circuit terminal 3 at the P43 Collision Alert Indicators connector. ⇒ If 2 Ω or greater Repair the open/high resistance on circuit 4787. ⇓ If less than 2 Ω
  8. Test for less than 2 Ω between control circuit terminal 12 at the P16 Instrument Cluster connector and control circuit terminal 2 at the P43 Collision Alert Indicators connector. ⇒ If 2 Ω or greater Repair the open/high resistance on circuit 3885. ⇓ If less than 2 Ω
  9. Replace the P43 Collision Alert Indicators. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Driver Assistance Systems Component Replacement Reference Control Module References for control module replacement, programming, and setup